Environmental concerns have prompted the U.S. government to push the auto industry to continue efforts to reduce harmful emissions and improve cars’ fuel economy. Both American and Japanese companies are producing hybrid car models, which combine a gasoline-powered combustion engine and a battery-powered electric motor. Hybrid cars have good gas-mileage, and some models get 20 to 30 more miles to the gallon (9-13 km/liter) than traditional cars. Research is being conducted on fuel-cell-powered vehicles. If successful, such vehicles could eliminate environmentally-harmful exhaust emissions.